1. Field of the Invention
The present invention relates to an internal combustion engine system including a fuel tank, an engine, a muffler, and others and relates to a method for controlling the internal combustion engine system.
2. Related Art
An HV (hybrid vehicle) and a PHV (plug-in hybrid vehicle) consuming less fuel are slow in the fuel consumption pace, and therefore there is a possibility that the fuel is stored in a fuel tank for a long period and thus deteriorates (oxidizes). Particularly, fuel (gasoline) including alcohol is apt to deteriorate rapidly. Deterioration of the fuel could cause deterioration of resin-made components and rubber-made components which are in contact with the fuel and cause corrosion of metal parts being in contact with the fuel. Further, there are concerns that oxidation products due to corrosion of the metal parts could adhere to an electrode and a contact to cause faulty electrical continuity and that the oxidation products could clog a filter.
In response to the above problem, a first conventional art provides a technique that inert gas such as nitrogen gas is filled in a fuel tank from an external high-pressure nitrogen cylinder. However, this technique requires an extra facility for periodically refilling the nitrogen gas in the high-pressure nitrogen gas cylinder, leading to a cost increase. Further, a vehicle requires an extra space for mounting the high-pressure nitrogen cylinder. Mounting the high-pressure nitrogen cylinder on the vehicle also leads to a problem of vehicle safety.
As a second conventional technique, the exhaust gas discharged from an engine is cooled by a cooler and temporarily stored in a reservoir, and after that, the exhaust gas is filled in a fuel tank from the reservoir by a pump. However, this technique requires various components such as the cooler, the reservoir, and the pump, leading to a cost increase. Further, a vehicle needs to have a mounting space for these components, which could cause restrictions on a vehicle design.
Herein, Patent Document 1 discloses a system for preventing oxidation of fuel by introducing exhaust gas to a fuel tank.